SYDNEY, Australia  The rate at which humans are pumping carbon dioxide into the atmosphere has more than doubled since the 1990s, according to Australian research, the latest report warning about the high rate of emissions accumulating in the atmosphere.

Findings published by Australia's Commonwealth Scientific and Industrial Research Organization also showed that 2005 marked the fourth-consecutive year of increased carbon dioxide emissions.

"To have four years in a row of above-average carbon dioxide growth is unprecedented," Paul Fraser, a scientist with the CSIRO's center for marine and atmospheric research, said in a statement.

The study analyzed a 30-year record of air samples collected at an Australian Bureau of Meteorology observation station on the southern island state of Tasmania.

Mike Raupach, a scientist with the organization, said from 2000 to 2005 the growth rate of carbon dioxide emissions was more than 2.5 percent per year, whereas in the 1990s it was less than 1 percent per year.

Raupach, who is also co-chairman of the Global Carbon Project, said 7.85 billion tons of carbon passed into the atmosphere last year, compared to 6.67 billion tons in 2000.

About half of all carbon dioxide emissions remain trapped in the atmosphere, and the rest are absorbed by the land and oceans, Raupach said. As emissions rise, so does the amount of carbon in the air.

Earlier this month, the World Meteorological Organization reported the level of carbon dioxide in the atmosphere reached 379.1 parts per million in 2005, more than 35 percent higher than in the late 18th century.

Raupach and Fraser presented their findings last week at an annual science meeting at Tasmania's Cape Grim Baseline Air Pollution Station.